Crankshaft and Bearings Cleaning and Inspection: Notes

Tools Required

• J 7872  Magnetic Base Dial Indicator
• J 43690  Rod Bearing Clearance Checking Tool. See Special Tools and Equipment .
• J 45059  Angle Meter. See Special Tools and Equipment .

CAUTION: Refer to Safety Glasses Caution in Cautions and Notices.
IMPORTANT: Use care when handling the crankshaft. Avoid damage to the crankshaft bearing surfaces.
1. Clean the crankshaft in cleaning solvent. Remove all sludge or restrictions from the oil passages.
2. Dry the crankshaft with compressed air.
Fig 1: Crankshaft
Courtesy of GENERAL MOTORS CORP.
3. Clean the crankshaft bearings in cleaning solvent. Wipe the crankshaft bearings clean with a soft cloth, do not scratch the crankshaft bearing surfaces.
4. Dry the crankshaft bearings with compressed air.
Fig 2: Crankshaft Bearings
Courtesy of GENERAL MOTORS CORP.
5. Inspect the crankshaft for the following:
   • Crankshaft journals (1) should be smooth with no evidence of scoring or damage.
   • Deep grooves (2)
   • Scratches or uneven wear (3)
   • Pitted surfaces (4)
   • Wear or damage to the thrust journal surfaces
   • Scoring or damage to the rear seal surface
   • Restrictions to the oil passages
   • Damage to the threaded bolt holes
Fig 3: Identifying Different Crankshaft Journal Wear Patterns
Courtesy of GENERAL MOTORS CORP.
6. Inspect the crankshaft balancer key (1), the keyway (2), and the threaded hole (3) for damage.

   Repair or replace the crankshaft as necessary.

Fig 4: Crankshaft Balancer Key, Keyway & Threaded Hole
Courtesy of GENERAL MOTORS CORP.
7. Measure the crankpins for out-of-round and taper. Refer to Engine Mechanical Specifications .
Fig 5: Measuring Crankpins For Out-Of-Round & Taper
Courtesy of GENERAL MOTORS CORP.
8. Use a suitable support to support the crankshaft on the front and rear journals.
9. Use the J 7872  in order to measure the crankshaft journal runout. The proper crankshaft journal runout is 0.025 mm maximum (0.0010 in maximum).
Fig 6: Measuring Crankshaft Runout
Courtesy of GENERAL MOTORS CORP.
10. Measure the crankshaft end play.
    IMPORTANT: In order to properly measure the crankshaft end play, the crankshaft, the crankshaft bearings, the crankshaft bearing caps, and the crankshaft bearing cap bolts must be installed into the engine block and the bolts tightened using J 45059  . The proper crankshaft bearing cap bolt tightening specification first pass is 20 N.m (15 lb ft), final pass is 73 degrees.
    1. Firmly thrust the crankshaft first rearward, then forward. This will align the crankshaft rear bearings and the crankshaft thrust surfaces.
    2. With the crankshaft pushed forward, insert a feeler gage between the crankshaft and the crankshaft bearing surface and then measure the clearance. The proper crankshaft end play clearance specification is 0.050-0.20 mm (0.002-0.008 in).
    3. Turn the crankshaft to check for binding. If the crankshaft does not turn freely, then loosen the crankshaft bearing cap bolts, one crankshaft bearing cap at a time, until the tight crankshaft bearing is located.

       Burrs on the crankshaft bearing cap or engine block, foreign matter between the crankshaft bearing and the crankshaft bearing cap or the engine block, or a faulty crankshaft bearing could cause a lack of clearance between the crankshaft and crankshaft bearing.

    Fig 7: Measuring Crankshaft End Play
    Courtesy of GENERAL MOTORS CORP.
11. Inspect the crankshaft bearings for craters or pockets. Flattened sections on the crankshaft bearing halves also indicate fatigue.
Fig 8: Identifying Crankshaft Bearing Craters Or Pockets
Courtesy of GENERAL MOTORS CORP.
12. Inspect the crankshaft bearings for excessive scoring or discoloration.
Fig 9: Identifying Connecting Rod Bearing Scoring Or Discoloration
Courtesy of GENERAL MOTORS CORP.
13. Inspect the crankshaft bearings for dirt or debris imbedded into the crankshaft bearing material.
14. Inspect the crankshaft bearings for improper seating indicated by bright, polished sections of the crankshaft bearings.
    • If the lower half of the crankshaft bearing is worn or damaged, both the upper and lower halves of the crankshaft bearing should be replaced.
    • Generally, if the lower half of the crankshaft bearing is suitable for use, the upper half of the crankshaft bearing should also be suitable for use.
Fig 10: Crankshaft Bearing Polished Sections (Improper Seating)
Courtesy of GENERAL MOTORS CORP.